This disclosure relates to methods for etching features in substrates, including etching features in silicon wafers and semiconductor substrates.
The fabrication of integrated circuits (IC) in the semiconductor industry typically involves using a plasma reactor to create plasma that assists surface chemistry used to remove material from—and deposit material on—a substrate. Dry plasma etching processes are routinely used to remove or etch material along fine lines or within vias or at contacts patterned on a semiconductor substrate. A successful plasma etching process requires an etching chemistry that includes chemical reactants suitable for selectively etching one material while not etching another material or not substantially etching another material.
For example, on a semiconductor substrate, a relief pattern formed in a mask layer can be transferred to an underlying layer of a selected material using a plasma etching process. The mask layer can comprise a light-sensitive layer, such as a photoresist layer, having a pattern formed using a lithographic process. Once the relief pattern is formed, the semiconductor substrate is disposed within a plasma processing chamber, and an etching chemistry feeds a plasma such that products of the plasma selectively etch the underlying layer while minimally etching the mask layer. This etch chemistry is produced by introducing an ionizable, dissociative gas mixture having parent molecules comprising molecular constituents that react with the underlying layer while minimally reacting with the mask layer/relief pattern. Production of the etch chemistry comprises introduction of a gas mixture and formation of plasma when a portion of the gas species present are ionized following a collision with an energetic electron. Heated electrons can serve to dissociate some species of the gas mixture and create a reactive mixture of chemical constituents (of the parent molecules).
With ionized gas species and a reactive mixture of chemical constituents provided, various features (e.g., trenches, vias, contacts, etc.) can be etched in exposed regions of the semiconductor substrate. Typical materials that are etched include silicon oxide (SiOx), silicon nitride (SiNy), poly-crystalline silicon (polysilicon), mono-crystalline silicon (silicon), and doped and un-doped silicon, for example.